Various gearing arrangements have been proposed which increase the output torque of the driven component of a system in relation to the input torque by control of the input-to-output gear ratio.
U.S. Pat. Nos. 2,122,330; 3,156,136; and 4,321,842 disclose rotary gear drive systems in which an internal rotary frame or cage is arranged within a case and carries one or more input and output planet gear sets. The output planet gears are meshed with a stationary sun gear. The input planet gears are spaced from a common central drive gear on the input shaft and are coupled for driven rotation by endless chains or intermediate spur gears. It is believed that for such systems employing the chainless idler spur gear drive connection between the driven gear and planet gears (both which are likewise spur gears), that an amount of torque that could otherwise be transmitted to the output shaft is lost on account of the idler gears acting, in effect, like sun gears during operation. It has been observed that the idler gears are caused to orbit about the drive gear with the cage but that they do not themselves rotate relative to the fixed case. It is believed that such lack of rotation of the spur-type idler gears accounts for the reduced torque transfer.
It is an object of the present invention to provide a chainless gear drive system that overcomes the above disadvantages.